
Lake Shore Model 325 Temperature Controller User’s Manual
Installation
3-9
Boosting Output Power (Continued)
The resistor must be chosen to convert a full scale current from the highest heater output range being used to the full
scale programming voltage of the auxiliary supply. For example, if the auxiliary supply has a full scale programming
voltage of 10 V and the maximum current for the highest heater output range being used is 0.3 A the programming
resistor should be 10 V / 0.3 A = 33
. The programming resistor must be rated for the power being dissipated in it,
which is:
Power = I
output
2
× R
program
or 3 W. The “Low” heater output range can be selected to reduce the power dissipated in the programming resistor.
3.7
INITIAL SETUP AND SYSTEM CHECKOUT PROCEDURE
The following is an initial instrument setup and checkout procedure. The intent is to verify basic operation of the unit
before beginning use for measurements. The procedure assumes a setup with two Lake Shore DT-470 Silicon diode
Sensors, one control loop, a single 50
heater, all readings in kelvin, and running in a liquid nitrogen environment.
CAUTION:
Check power source for proper voltage before connecting the line cord to the Model 325.
Also check the line voltage setting on the window in the fuse drawer. Damage to unit may
occur if connected to improper voltage.
1. Check power source for proper voltage. The Model 325 operates with 100, 120, 220, or 240 (+6%, –10%) AC input
voltage.
2. Check window in fuse drawer for proper voltage setting. If incorrect, refer to Section 8.4.
3. Ensure the power switch is in the off (
O
) position.
CAUTION:
The sensor must be connected to the rear of the unit before applying power to the
Temperature Controller. Damage to the sensor may occur if connected with power on.
4. Verify your sensor installation in the liquid nitrogen environment. Then plug the control sensor connector in INPUT
A and the sample sensor connector in INPUT B. Details of sensor hardware connections are detailed in Section 3.4.
5. Connect the heater to the banana jacks labeled HEATER OUTPUT. A 50
heater allows the maximum power
output of 25 W if the heater resistance setting is set to 50
. A 25
heater allows the maximum power output of
25 W if the heater resistance setting is set to 25
. Details of heater installation are in Sections 2.4 and 3.6.
6. Ensure any other rear panel connections are connected before applying power to the unit. This includes the RS-232
(Section 6.2.1) and IEEE-488 (Section 8.7.2) connectors.
7. Plug line cord into receptacle.
8. Turn the power switch to the on (
l
) position. The front panel will briefly display the following.
Lake-Shore-Model-325
--Temp.-Controller
9. The typical display shown below will now appear.
À- 77.35½-Á- 77.35½
 -0.000½----0%-Off
The front panel display is divided into four areas. The default display settings place the Sensor A reading in the upper
left, the Sensor B reading in the upper right, the Setpoint in the lower left, and the heater output of Loop 1 (in percent) in
the lower right. All temperature readings are in kelvin. Each of these display areas is individually configurable by
pressing the
Display Format
key and following the instructions in Section 4.3.
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